Multinuclear NMR Investigation of Methylaluminoxane Full article
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Macromolecular Chemistry and Physics
ISSN: 1022-1352 , E-ISSN: 1521-3935 |
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| Output data | Year: 1997, Volume: 198, Number: 12, Pages: 3845-3854 Pages count : 10 DOI: 10.1002/macp.1997.021981206 | ||||
| Tags | OLEFIN POLYMERIZATION; CATALYSTS | ||||
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| Affiliations |
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Funding (1)
| 1 | Russian Foundation for Basic Research | 97-03-32546 |
Abstract:
By means of 27Al, 1H, 17O and 13C NMR spectroscopy the structure of the methylaluminoxane (MAO) cocatalyst of Kaminsky-Sinn catalysts was investigated. We have found that the 27Al NMR resonance line of MAO is extremely broad at room temperature (δ ≈ 60, Δω1/2 50 ± 10 kHz). At elevated temperatures (40–120°C) MAO exhibits an 27Al resonance at δ 110 ± 10, Δω1/2 15–10 kHz, that is, within the range reported for the aluminoxane clusters [(t-Bu)Al(μ3-O)]6 and [(t-Bu)Al(μ3-O)]9 with cage structures. The 27Al resonance at δ 149–153, usually attributed to MAO, belongs to AlMe3 present in MAO samples. The 17O NMR resonance of MAO at 50°C (δ 67, Δω1/2 1.7 kHz) is within the range typical for three-coordinate oxo ligands, but it can be attributed only to a minor part of MAO oligomers. It was shown that the intensity of 27Al and 17O NMR resonances of MAO increases with increasing temperature, whereas the width of both resonances is almost constant. The results obtained lead to the conclusion that at ambient conditions MAO forms oligomers (MeAlO)n with cage structure and MeAlO3 environment. Upon increasing the temperature these oligomers reversibly break into smaller MAO units. Based on the 27Al NMR data the average radius (R) of MAO oligomers is approximately 5.1 ± 0.3 Å at 120°C. This radius corresponds to (MeAlO)n species with 9 < n < 14. At ambient conditions the predominant part of MAO forms oligomers with R = 7 ± 0.5 Å and 20 < n < 30.
Cite:
Babushkin D.E.
, Semikolenova N.V.
, Panchenko V.N.
, Sobolev A.P.
, Zakharov V.A.
, Talsi E.P.
Multinuclear NMR Investigation of Methylaluminoxane
Macromolecular Chemistry and Physics. 1997. V.198. N12. P.3845-3854. DOI: 10.1002/macp.1997.021981206 WOS Scopus РИНЦ ANCAN OpenAlex
Multinuclear NMR Investigation of Methylaluminoxane
Macromolecular Chemistry and Physics. 1997. V.198. N12. P.3845-3854. DOI: 10.1002/macp.1997.021981206 WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | Apr 18, 1997 |
| Published print: | Dec 1, 1997 |
| Published online: | Mar 12, 2003 |
Identifiers:
| Web of science: | WOS:000071129000006 |
| Scopus: | 2-s2.0-0000477672 |
| Elibrary: | 13262019 |
| Chemical Abstracts: | 1997:812607 |
| Chemical Abstracts (print): | 128:53718 |
| OpenAlex: | W2040968511 |